The objective of this research study is to evaluate a new, experimental drug called FLOCOR (Purified Poloxamer 188) in reducing the duration of vaso-occlusive crises in patients with sickle cell disease (SS, SC or sickle-thalassemia). The study will also determine if this drug helps to shorten duration and intensity of pain, analgesic use, length of hospitalization, and to determine the pharmacokinetics and pharmacoeconomics of the drug in sickle cell patients in crises. This drug has been studied in about 3,000 patients with heart attacks and in about fifty patients with sickle cell disease. The study will involve a 72-hour period of hospitalization, over which time patients qualifying for inclusion criteria, and lacking all of the exclusion criteria, will be randomized at the time of pain crisis to one of two arms, placebo or the drug FLOCOR arm. They will then receive a one hour loading intravenous dose (100mg/kg) of the study drug or placebo followed by a continuous 47 hour intravenous infusion (30mg/kg/h) of the study drug or placebo. Patients must begin receiving the study drug infusion with 12 hours from presentation to Howard University Hospital with a vaso-occlusive crisis and as soon as possible after randomization, preferably with two hours. Pain evaluations will be made during treatment, post-treatment, and also at followup. Patients will be monitored for 24 hours after infusion. If the crises has not resolved within 72 hours, patients will remain in the hospital. This is a double-blind study, half of the patients in the study will receive the drug and the other half, only salt water. Neither the nurse or the doctor will know which one of the patient will receive. The standard treatment for patients with sickle cell disease will be followed (pain medication, IV fluids, etc.) with the exception of medications such as Motrin (ibuprofen), aspirin and related drugs which may cause side effects when given with FLOCOR. This treatment aims to offer relief of the symptoms of sickle cell disease.